Isaiah 18

18:2 That sendeth ambassadors by the sea, even in vessels of bulrushes upon the waters, saying, Go, ye swift messengers, to a nation scattered and peeled, to a people terrible from their beginning hitherto; a nation meted out and trodden down, whose land the rivers have spoiled!

That sendeth ambassadors

The local reference is evidently to an embassy from Egypt, resulting in the alliance denounced in Is. 30., 31., Jeremiah 37:7-11 .